The phosphoric acid fuel cell is known as one of most researched, and commercially most advanced types of fuel cell. An advantage it holds over NAFION-based fuel cells is the higher temperature range of operation permitted by the electrolyte. Electrolytes in phosphoric acid fuel cells have been used up to 160° C. before water loss, to form pyrophosphoric acid, leads to reduced conductivity and poorer performance.
Proton exchange membrane fuel cells (PEMFCs) are under intense development as non-polluting power sources that in principle are the most efficient means of converting chemical energy to electrical energy and mechanical work. However, practical realization of this efficiency, even in the simple H2/O2 fuel cell case, proves to be fraught with difficulties. NAFION fuel cells, based on sulfonated polytetrafluoro-ethylene proton conductive membranes, are favored for their high conductivities, but are limited to temperatures below 100° C. because of loss, at higher temperatures, of the water needed for high conductivity—which means the fuel cell is susceptible to catalyst poisoning by CO gas impurities. The NAFION-based cells also suffer from acute water crossover, hence water management, problems.
Attempts have been made to increase the operating temperature of the NAFION membrane cell by various methods. However, NAFION and other perfluorinated polymer electrolytes (i.e. FLEMION, and ACIPLEX) are limited in commercial applications because of the high materials costs, coupled with the reduced performance at high temperatures.